Fifty years ago, the first major trials of an oral contraceptive produced a pill that gave women control over their fertility for the first time. This week the next big leap for womankind was heralded with the reporting of trials of the first major new pill to provide protection against pregnancy - without scary side-effects. The new generation of the pill, should it live up to the scientists' hopes and justify the "Super pill" and "Wonder drug" headlines, will control women's fertility while reducing the major risks of breast cancer, thrombosis and heart disease associated with the current pill. All this as well as stopping periods, potentially freeing women of PMT.

There was much excitement but also increasingly desperate notes of caution from those in the frontline of family planning. "We would be disappointed if this new pill made people think the current pill is unsafe," says Toni Bellfield, director of information at FPA, formerly the Family Planning Association.

The worries about the existing pill - combined, mini or otherwise - are already enough to make many women feel they should not take any oral contraceptive for too long. So when they hear about the so-called "dream pill" the verdict is predictable: It sounds fantastic ... what's the catch?

The first is that scientists believe it will be at least another five years - and probably more like 10 -before it's on the market. And who is to say the product will live up to the hype? The current hoo-ha is based on trials of fewer than 200 women. It's a small sample and more detailed studies may have an altogether gloomier outcome.

The second is FPA's question: what's wrong with the existing pill? Should women, for example, be worried about the breast cancer link? Studies show that breast cancer rates increase by 24% among women who have been taking an oral contraceptive in the past 10 years - though the heightened risk is thought to disappear 10 years after a woman stops taking the pill.

Anna Glasier, director of sexual and reproductive health at the University of Edinburgh, says the figures can be misleading. "Women who are on the pill are younger, and therefore at very slight risks of these illnesses to begin with. An increase of 24% in breast cancer does not amount to huge numbers of women."

So for every 10,000 women who take the pill for five years, an extra one or two cases of breast cancer will be diagnosed in those who stop at 25, four to five in those who stop at 30 and an extra 11 in those who stop at 35.

The risk of thrombosis ( blood-clotting) is about 300% higher among women who are on the pill compared with those who aren't. "Yes, the risk of thrombosis is three times higher, but if you're pregnant it's six times higher and what you're trying to avoid when you're on the pill is getting pregnant," says Glasier. "It's safer to be on the pill than pregnant."

The women who might be worried about this - those who are overweight, smoke or have a history or diagnosis of high blood pressure - might benefit from the new drug, but are already offered the progestogen-only pill, which reduces those risks.

Osteoporosis has been linked to the injected hormonal contraceptive Depo-Provera. But most studies suggest the oestrogen in the pill actually provides some protection against bone thinning, something the new pill does not seem to offer. The protection the current pill gives against cancers of the womb, ovaries and perhaps now the bowel are also proven - but not in the new pill.

As for the excitement over the prospect of doing away with menstruation? It's not actually a terribly new idea. The current pill requires a seven-day break once a month when bleeding - though not a full period - occurs, but can already be safely taken without that break, something many women opt to do at their convenience (a so-called period holiday). Many women who opt for Depo-Provera stop menstruating altogether, for up to 18 months after their final injection wears off. A new pill being sold in the US is Seasonale, which is taken for 84 days straight with a break four times a year for your seasonal period: the spring, summer, autumn and winter bleeds.

What the new contraceptive may be able to do is reduce the slight risk from the old pill of breast cancer, thrombosis and heart disease and suspend periods. There is also no sporadic bleeding, which can occur with the progestogen-only pill. But what else it does, what new side-effects it might bring further along the line, have not been investigated.

Perhaps the real struggle with the pill 50 years on is not so much about its potentially deadly side-effects, but its day-to-day impact on women's lives. Alice Walker, a 27-year-old social worker from Bristol, has chopped and changed her pill over the years according to her relationship status but also how they made her feel. Her worry isn't necessarily about breast cancer or heart disease, but her moods, her libido and how it affects her weight.

"I came off it and lost half a stone in two weeks. Libido definitely goes down. Doctors will let you change if it gives you headaches, but you're not encouraged to if you're not obese but worried about weight. I'd prefer to be on the pill the whole time, but only if it didn't have all these effects."

The problem is that every pill has a slightly different effect on individual women's hormones, and hormones, bundled up as they are in emotions and moods, react differently from person to person. Every drug has side-effects, so perhaps the idea of a problem-free pill is a wild goose chase.

Kay Wellings, professor of sexual and reproductive health research at the London School of Hygiene and Tropical Medicine, says the decisions women make about contraception are an incredibly complex trade-off between risks and benefits.

"If you're hellbent on not getting pregnant you'll put up with the odd headache, or a couple of pounds gained in weight won't mean much to you. You weigh up the pros and cons, as you do with every medicine. All medicines are just useful poisons."